The human oral cavity contains one of the most densely populated and complex mixed microbial floras that inhabit the human body (Takhashi, N., 2005). One major component of the oral mixed microbial flora is comprised of fermentable carbohydrate metabolizing types of microorganisms that are found particularly in supra-gingival dental sites, namely tooth pits, fissures, and interproximal tooth embrasures. Fermentable dietary carbohydrates and corresponding fermentative oral bacteria are easily and regularly retained in many of these intra-oral locations, sheltered from saliva and readily able to interact to produce abundant acidity and an acidic pH. Such acidity is principally due to the generation of lactic acid, an entity that can readily solubilize tooth calcium phosphate, the dominant mineral element comprising the mineralized tissues (i.e., enamel, dentin, and cementum) of human teeth.
In contrast to acidity, if the environment of the teeth gingivae is alkaline (e.g., because of elevated urea levels that occur in many individuals' gingival crevicular fluid), alkaline conditions may be expected to prevail around the necks of the teeth to where, instead of dental caries, dental calculus and/or periodontitis indices are more evident.
The dental calculus/periodontitis entity involves a mixed microbial flora that mainly populates the regions around the necks of the teeth and extends into adjacent gingival and subgingival dentition sites. The bacteria involved in these locations are mainly non-fermenting. They have been proven to be largely comprised of proteolytic, putrefactive microorganisms that readily metabolize nitrogenous substrates, particularly such derived from the gingivae and adjacent gingival crevicular and periodontal pocket fluids and tissues (Takhashi, N., 2005). Of particular note is that this includes involvement with urea and amino acids, the main end-products of the numerous, common human body amino acids that circulate in the blood vessels throughout the human body. These amino acids and ammonia related thereto are degraded by enzymes in bacteria readily found in gingival crevicular fluid (Golub, L. M., Borden, S. M., and Kleinberg, I., 1971; Onosi, M., Tachibana, Y., Nakamura, T., Takakuwa, S., and Ishioka, K., 1957; Singer, D. L. and Kleinberg, I., 1978).
Upon microbial degradation, gingival and periodontal crevices containing urea are conducive to bacterial degradation to ammonia and can exhibit a high alkaline pH. Such a high pH is an essential element responsible for the easy formation of calcium phosphate deposits (generally referred to as dental plaque or calculus), which readily form around the base of the crowns of teeth (Denepitiya L. and Kleinberg I., 1982; Arch. Oral Biol.; Salako, N. O. and Kleinberg, I., 1989; Jin, Y. and Yip, H.-K., 2002). Left untreated, these crevices promote the proliferation of additional ureolytic and proteolytic bacteria, which in turn promote the formation of additional calculus. Ultimately, this can cause the development of periodontal disease (e.g., gingivitis) (Jacobson, M. and Kesel, R. G., 1950). Central to these processes are the formation and flow of gingival/periodontal crevicular fluid (Golub, L. M., Borden, S. M., and Kleinberg, I., 1971), which characterizes and helps perpetuate these periodontal disease conditions by maintaining a high pH in the environment.
We have previously shown that amino acids can serve as important bacterial substrates and can thereby help facilitate both the accumulation of dental plaque and the development of periodontal disease (including gingivitis, with symptoms including bleeding gums and putrefactive gingivae). For example, urea has been demonstrated to promote tooth and gingival alkalinity, enhancing the accumulation of plaque-causing bacteria on teeth and other surfaces in the oral cavity (Kleinberg, I., 1967, Arch. Oral Biol., 1475-1484). Numerous other amino acids can serve as nitrogenous substrates that contribute to varying degrees of alkalinity and promote periodontal disease, albeit to a lesser degree than urea (Biswas, S. D. and Kleinberg, I., 1971; Golub, L. M., Borden, S. M., and Kleinberg, I., 1971; Kleinberg, I. and Hall, G., 1968). In general, amino acids function to maintain a balance of alkalinity in the oral cavity.